Has anyone ever encountered a drive with a write cache that actually *helped*? I haven't. As in: would it be a good idea for the OSD to just disable the write cache on startup? Worst case it doesn't do anything, best case it improves latency. Paul -- Paul Emmerich Looking for help with your Ceph cluster? Contact us at https://croit.io croit GmbH Freseniusstr. 31h 81247 München www.croit.io Tel: +49 89 1896585 90 On Wed, Jun 24, 2020 at 3:49 PM Frank R <frankaritchie@xxxxxxxxx> wrote: > fyi, there is an interesting note on disabling the write cache here: > > > https://yourcmc.ru/wiki/index.php?title=Ceph_performance&mobileaction=toggle_view_desktop#Drive_cache_is_slowing_you_down > > On Wed, Jun 24, 2020 at 9:45 AM Benoît Knecht <bknecht@xxxxxxxxxxxxx> > wrote: > > > > Hi Igor, > > > > Igor Fedotov wrote: > > > for the sake of completeness one more experiment please if possible: > > > > > > turn off write cache for HGST drives and measure commit latency once > again. > > > > I just did the same experiment with HGST drives, and disabling the write > cache > > on those drives brought the latency down from about 7.5ms to about 4ms. > > > > So it seems disabling the write cache across the board would be > advisable in > > our case. Is it recommended in general, or specifically when the DB+WAL > is on > > the same hard drive? > > > > Stefan, Mark, are you disabling the write cache on your HDDs by default? > > > > Cheers, > > > > -- > > Ben > > _______________________________________________ > > ceph-users mailing list -- ceph-users@xxxxxxx > > To unsubscribe send an email to ceph-users-leave@xxxxxxx > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx > To unsubscribe send an email to ceph-users-leave@xxxxxxx > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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